The objectives are to investigate the nature of human red cell receptors and to establish their distribution and the movement resulting from the action of antibodies, drugs and the effects of aging in vivo and in vitro. Gold-labeled antibodies and electron microscopy are used for these following phenomena. Isolated erythrocyte vesicles and ghosts are solubilized by various methods and the SDS-PAGE patterns are used to identify the changes occurring in the membrane proteins. Inhibition studies using detergent solubilized extracts of red cell stromata are used to localize blood group antigen activity.